Method of and apparatus for separating tobacco



March 14, 1967 H. HARTE ETAL 3,308,950

METHOD 0F AND APPARATUS FOR SEPARATING TOBACCO Filed May '7, 1965 5 Sheets-Sheet 1 if l 51 o l A 1?.: 8 Fig! fmfenars @W7 @M March 14, 1967 H, HARTE ETAL 3,308,95

METHOD OF AND APPARATUS FOR SEPARATING TOBACCO Filed May 7, 196.3 5 Sheets-Sheet 2 March 14, 1967 Filed May '2, 1963 H. HARTE ETAL METHOD OF AND APPARATUS FOR SEPARATING TOBACCO 5 Sheets-Sheet 5 March 1 4, 1967 H. HARTE ETAL. 3,308,950

METHOD OF AND APPARATUS FO-R SEPARATING TOBACCO Filed May 7, 1965 5 Sheets-Sheet 4 Fig.

Inventors m afd* 14, w57 H. HARTE ETAL v 3,308,950

METHOD OF ND APPARATUS FOR SEPARATING TOBACCO Filed May v, 196s 5 Sheets-sheet s United States Patent Utilice Patented Mar. 14, 1967 3,368,950 METHOD @F AND APPARATUS FR SEPARA'HNG TQBACC Heinz Harte, Hamburg-Bergedorf, Johannes lwen, Reinhek, and Waldemar Wochnowslri, Hamburg, Germany, assignors to Hanni Werke Krber t Co. KG., Hamburg-Bergedorf, Germany Fiied May 7, 1963, Ser. No. 278,688 Claims priority, appiication Great Britain, May 9, 1962, 17,823/62 Claims. (Cl. 269-137) The present invention relates to a method of and to an apparatus for separating lighter particles from heavier particles which together form a mixture, and more particularly to a method of and to an apparatus for separating tobacco ribs from tobacco leaves in a continuous operation.

Certain conventional separating apparatus of which we have knowledger at this time operate with acceptable ethciency if the rate at which the mixture is admitted thereto is maintained within a rather narrow range. However, if the rate of feed drops below or rises above such range, the eiiiciency of the apparatus drops immediately which is observable in low output or in excessive percentage of heavy particles in the stream of separated lighter particles. The rate of feed varies for a variety of reasons, for example, because the stripping device does not deliver a constant stream of leaves and ribs or because the separators are connected in series and the output of a given separator iiuctuates.

Accordingly, it is an important object of our. invention to provide an apparatus whose e'liciency is greater than the eiiiciency of conventional apparatus, which operates with high efficiency irrespective of fluctuations in the rate at which a mixture of lighter and heavier particles is being fed thereto, and which may be readily adjusted to operate with optimum efficiency in connection with different types of mixtures, i.e., with mixtures which might contain varying percentages of lighter particles.

Another object of the invention is to provi-de a separating apparatus of the just outlined characteristics which may be directly coupled with a conventional stripping device and which may carry out the separation of lighter particles in a single operation or in a series of consecutive operations, especially when it is desired to collect all of the lighter particles. l

A further object of the invention is to provide an irnproved method of separating lighter tobacco particles from tobacco ribs and similar heavier particles.

An additional object of the invention is to provide a method according to which the lighter particles may be separated in a very compact apparatus and according to Whi-ch the percentage of heavier particles in the stream of lighter particles obtained upon separation of the mixture may be varied within a desired range.

With the above objects in view, one feature of our invention resides in the provision of a method of separating lighter particles from heavier particles which together form a mixture of lighter and heavier particles, particularly for separating tobacco ribs from tobacco leaves. The method comprises the steps of introducing a continuous thin stream consisting of a dilute mixture of lighter and heavier particles into an ascending non-vertical highvelocity current of air, reducing the speed of the stream by permitting gradual expansion of the current whereby some of the heavier particles descend by gravity and leave the air current, dividing the remainder of the mixture into a plurality of partial streams and advancing each partial stream in an upwardly extending path with currents of air which are strong enough to entrain the lighter particles but which are too weak to entrain the heavier particles so that the heavier particles tend to descend and form a further stream constituting a thin 'barrier which moves transversely of the ascending current to hinder the entry of heavier particles into the paths of partial streams but which permits some air and the lighter particles to penetrate therethrough, and withdrawing this further stream which mainly consists of a thin layer of heavier particles from the air currents so that the streams advancing in the upwardly extending paths consist exclusively or almost exclusively of lighter particles.

In accordance with another feature of our invention, after its separation from the air currents the stream of heavy particles which forms a barrier against the entry of heavier particles into the upwardly extending paths for the partial streams may be subjected to the action of an ascending current of air which entrains only lighter particles in the event that some lighter particles have been caused to advance with the heavies. The thus obtained additional stream of lighter particles may be merged with the streams which advance in the upwardly extending paths to obtain a single stream of lighter particles. Analogously, all of the heavier particles may be merged into a single stream which may be subjected to a second separating action in the same way as described above in order to separate therefrom all such lighter particles which stitll remain in the stream of heavy particles.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved separating apparatus itself, however, both as to its construction and its method of operation, together with additional features and advantages thereof, will be best understood from the following detailed description of a specific embodiment with reference to the accompanying drawings, in which:

FlG. 1 is a perspective view of a separator assembly which includes two groups of separators and which is shown from the rear side thereof;

FIG. 2 is a perspective view of the front side of the separator assembly;

FIG. 3 is a schematic view of the interior of one group of separators substantially as seen in the direction of arrow A in FIG. 1;

FIG. 4 is a schematic view of various tobacco streams which develop upon separation of a specific mixture of lighter and heavier tobacco particles in the interior of the separator group shown in FIG. 3; and

FIG. 5 is a schematic diagram showing the eiciency curves of a single separator group and of two separator groups for such specific mixture of lighter and heavier tobacco particles.

FIGS. 1 and 2 illustrate two sections or groups which together constitute a separating apparatus arranged to receive a mixture of tobacco ribs and tobacco leaves from a stripping device, not shown. Since the two groups are of identical construction, only one thereof will be described in greater detail by referring to FIGS. 1, 2 and 3.

Each group comprises a base frame ll having an upper frame member 11 which carries a first housing 2 and an upright frame member 12 which supports a second housing 3. The housing 2 accommodates the parts of a primary separator and the housing 2 accommodates the parts of a secondary separator. An intake 4 is connected to the lower end of the housing 2, and this lower end is also connected with an extractor duct 5. A collecting oli-take pipe 6 at the upper end of the primary housing 2 is fastened to a ange 61 which surrounds an opening 22 provided in the rear wall 23 of this housing. Inspection windows 24 and 2S are respectively movable in frames 26 and 27 which are fastened to and which surround openings provided in the rear wall 23. Actuating rods 62 and 63 which are shiftable by hand and which may be arrested in selected positions of adjustment are connected to flaps 64 and 65 on the take-olf pipe 6, see FIG. 1. The flaps 64 and 65 may admit currents of secondary air (false air) into the pipe 6 and respectively control the flow of air into take-off connections 66 and 67. A suction pipe 68 is connected to the pipe 6.

A supply pipe 41 which admits a mixture of ribs and leaves into the interior of the primary housing 2 is connected to the intake 4. A rotary cell wheel extractor 51 is attached to the extractor duct 5, and the drivenshaft 52 of this extractor is connected to a motor 55 through a chain drive 53 and a drive shaft 54. The driven shaft 71 of a second rotary cell wheel extractor 7 (see B1G. 3) receives motion from the drive shaft 54through a chain drive similar to the drive 53. The chain drives are shielded by a chain protector 56.

A collecting funnel S isattached to the cell wheel extractor 51 and opens into an olf-take pipe S1. A connecting member 82 which is xed to the funnel 8 is mounted at the lower end of the housing 3 whose upper end is connected with` an off-take pipe 9, the latter serving to convey leaves which are separated from ribs in the housing 3. The pipe 9 is connected to the rear wall 31 of the housing 3, and this rear wall is provided with openings covered by inspection windows 32, 33 which are movable in frames 34, 35. An actuating rod 91 which is adjustable by hand and which may be xed in selected positions of adjustment is 'coupled to a flap 92 (see FIG. 2) which serves to admit currents of secondary air (false air) into an off-take duct 93 attached to the pipe 9.

The off-take pipe 81 is connected to the intake 4 of the second separator group in the same way as the supply pipe 41 is connected to the intake 4 of the housing 2 shown in FIG. 3.

FIG. 2 illustrates the front wall`21 of ythe housing 2 and additional inspection windows 28, 29 which are provided on this front wall.' FIG. 2 also shows a connecting duct 73 between the cellwheel extractor 7 and the housing 3. Two additional inspection windows 37, 38 are provided on the front wall 36 of the housing 3.

FIG. 3 illustrates in schematic sectional view.one of theseparator groups shown in FIG. 1 as seen ,in they direction of arrow A. This illustration shows some of the previously described parts and the internal construction of the housings 2 andv 3. An inclined primary separator chamber 10 is provided in the lower part of the housing 2, and the inclination of this chamber is determined by a guide wall 101 and a guide surface 102.. A secondary air valve 103 is provided at the lower end of the wall 101, and this valve is adjustable and may be fixed in a selected position after each adjustment. Hereinafter, the primary separator chamber 10 will be referred to as the expansion space whose upper portion communicates with two air-oat separator channels 11, 12 andwhose lower portion lcommunicates with the intake 4. The channels 11, 12 are formed by a guide member or baffle 13 having a substantially triangular lower end portion 131 and guide surfaces 132, 133 which extend upwardly in arcuate paths to merge into substantially vertical surfaces 134, 135. The surface 134 terminates at the lower end of the take-off connection 66 for the air-oat separator channel 11, and the surface 135 terminates at the lower end of the take-olf connection 67 for the channel .12. The upper end portion of the intake 4 assumes the form of an inclined supply duct 42 whose imaginary `extension into the expansion space 10 leads into the channel 12.

The housing 3 denes a third air-float separator channel 14 whose central portion 141 opens into the -connecting duct 73. Guide walls 143 and 144 are provided in the lowerportion or zone 142 ofthe channel 14 for varying the cross-sectional area of this channel, and each of these guide walls is adjustable and may be fixed in a selected position of adjustment. The motor 55 which drives the cell wheel extractors 51 and 7 is mounted on the upright frame member 12.

4. i The method of our invention will now be described with reference to FIGS. 3 and 4.

The mixture Vof ribs and leaves is forced or projected at high speed in the direction indicated by an arrow 1S` and enters the expansion space, 10through the materialk supply pipe 41, through the-intake 4, and through the supply duct 42. The ascending air current which enters at 42 expands in the space `10 and forms a divergent funnel-shaped current whose outlines are indicated by dotted lines 16 and 17.

FIG. 4 shows the distribution of the ingredients of the original mixture which constitutes a specific mixture of leaves and ribs. The stream V represents the mixture which enters thefcharnber 10 at42 and whichcontains percent or all of the tobacco particles including the leaves and the ribs. Heavy tobacco particles forming a stream S1 will fall out of the-comparatively thin stream or layer V by leaving the path defined by the walls of the space 10 to enter the extractor duct 5, and the stream of heavies represented at S1 constitutes about 25, percent of the total amount of tobacco that is being admitted at 42. At a point above the deilecting surface111, the remaining portion VI of the original tobacco stream or layer V encounters a transverse stream M1 of heavy tobacco particles (ribs) which have fallen out of the airfloat separator channel 11k and which have been deflected by the surface 111 in the direction indicated by an arrow 18. The remainder V1 of the stream V (i.e., the stream V without the stream S1) and the air current flowing between the dotted lines 16, 17 will act on the heavy particles which form the stream M1 so that the stream M1 eventuallyy takes up some of the-leaves and advances in the direction indicated by anfarrow 19 to enter the cell wheel extractor 7. The stream M1 forms a retarding screen or curtain which slows down the lighter fractionof the stream V1 and which forms a barrier between the channels 11, 12 and the space 10 vso that the resulting mixed stream M1 consisting mainly of .additional heavy particles dissipates to a great extent the high kinetic energy of the stream V1. The additional heavier lparticles forming the mixed stream M1 consisting mainly of heavies descending from the chanel 11and in part from the channel 12 constitute about 21`percentof the stream V.

The particles which form the stream V1 and which pass through the screen formed by the transversely advancing stream M1 must again be accelerated in the region of the channels 11 and 12 so that, with corresponding adjustment of air dov/,one will obtain a very good separation effect. Streams B1 and B2 of pure leaf material are sucked olf through the channels 11 and 12, and these streams respectively constitute 9 percent and 15.5 percent of the total amount of tobacco that isfbeing admitted to the expansion space 10.

The heavies separated mainly from the stream B2 descend from the channel 12 toward the extractor 7 by forming a stream M2, and this stream merges with the stream M1 to form a stream S2 which descends in the chamber 14 and which merges with the` stream S1 to form a composite stream S, the latte-r being .withdrawn through the lower 'region 142 of the chamber 14. The stream M2 constitutesA about 29 percent of, the total amount of tobacco supplied to the space 10.

A further pure leaf fraction ,or stream B3 which constitutes about 20 percent of the original mixture (stream V) is being withdrawn through the upper end of the chamber 14 and enters the off-take duct 93. This stream B3 is entrained by the current of air ascending from the lower portion 142 of the chamber 14 toward the duct 93. Thus, the composite stream; B of :pure leaf tobacco (streams B1, B2 and B3) constitutes about 44.5 percenty of the specific mixture lV. This mixture is assumed to contain 25 percent of pure ribs, 7.5 percent of leaf material which adheres to the ribs (i.e., which was not ripped olf the ribs'in the stripper which rdelivers the mixture intothe supply pipe 41), and 67.5 percent of free leaf material. Thus, and since the stream B consisting of partial streams B1-B3 constitutes about 44.5 percent of the original mixture (stream V), the separator assembly of FIG. 3 can remove 67 percent of free leaf material in a single pass of the mixture therethrough.

FIG. 5 is a graph illustrating a stream of separated leaf tobacco with a rib proportion factor Rf of 0.7 percent. That is to say that the separated leaf material (streams B1-B3) contains 0.7 percent of heavies, the remainder being pure leaf material. This graph also shows that 67 percent of leaf material is extracted in a ysingle separator group which operates with the factor Rf of 0.7 percent. The heavy fraction which forms the st-ream S2 and which falls downwardly through the separator chamber 14 to merge with the stream S1 constitutes 30.5 percent of the total amount of tobacco admitted to the chamber. The partial stream S1 constitutes 25 percent of the mixture so that the stream S constitutes 55.5 percent of the stream V. The stream S is thereupon introduced into the second separator group (shown in the right-hand half of FIG. l or in the lefthand half of FIG. 2) wherein the separating action is repeated to remove additional pure leaf material from the stream S.

In FIG. 5, the ratio of the eiciency n to the rib proportion factor Rf for a given separator group (the first group) is indicated by a curve 20. A second curve 21 indicates the ratio of the efficiency 17 to the same rib proportion factor. The factor Rf (in percent) is shown along the X-axis, and the efficiency y is shown (in percent) along the Y-axis. The point marked 201 indicates that, with the single separator group of FIG. 3, one can achieve an eiiciency of 67 percent if the rib proportion factor is 0.7 percent. The point marked 211 on the curve 21 shows that, with the same factor Rf, the efhciency of an apparatus comprising two series-connected separator groups is 88 percent.

To our knowledge, the average eliciency of a stripping train including two or more separator groups of conventional construction is less than 70 percent. Thus, the output of our separator assembly is much higher than the output of all such assemblies which are known to us at this time and may reach as much as 1200 kg. In many instances, the rib proportion factor Rf may be much higher whereby the yield of a single separator group and also of the assembly of two or more groups is substantially higher. Thus, a single separator group will operate with an efficiency of 82 percent if the rib proportion factor is 2 percent and, if two separator groups are used by retaining the same rib proportion factor (Rf=2), the eiiciency of the assembly may reach, or even exceeds 96 percent.

If the amount of heavy material extracted by the wheel extractor 51 varies, the operator adjusts the position of the secondary air flap 103.

It is obvious that the stream S1 may be merged with the stream S2 at a point above the lower end of the channel portion 142 so that the current of air ascending through the channel 14 will entrain all or some of such lighter particles which might have passed through the extractor 51.

The surfaces of the bale 13 direct the heavy particles which form the streams M1 and M2 toward the second extractor 7. The valve 103 controls the amounts of heavier particles which form the stream S1 by admitting controlled quantities yof air into the lower portion of the space 10. The valves or aps 64, 65 and 92 serve an analogous purpose by regulating the iiow of air from the space and channel 14. It will be noted that the volume of the channel 14 is comparatively small because this channel need not receive all of the original mixture.

In accordance with a slight modification of the method described in connection with FIG. 3, the stream S2 may be introduced into the second housing 2 without passing through the housing 3.

Referring again to FIGS. 1 and 2, it will be noted that the housings 2 and 3 form a unit wherein the housings 3 alternate with housings 2. This is of importance because the entire appa-ratus occupies very little space which is at a premium in tobacco processing plants. If desired, the apparatus may comprise a third pair of housings 2, 3 so that the separating operation may be carried out in three stages. The housings 2 and the associated second housings 3 may be formed with common walls 2', see FIG. 3.

The current of ascending air admitted through the intake 4 may be generated vby a fan or the like whose pressure side is connected with' the supply pipe 41 and whose suction side is connected with the pipes 68 and 9. It is also possible to use two or more fans, one for each of the oiftake pipes 6, 9. Such connections between one or more fans and a separating apparatus are well known in the art and form no part of our invention.

A very important advantage of our method is that one can operate with very high outputs since, prior to the separation in a supporting air current (channels 11, 12 and 14), a great percentage of heavier tobacco particles is already removed from the air currents. Consequently, the separation by currents of air which carry only the lighter particles is more thorough and the percentage of heavier particles in the streams B1-B3 is negligible. Thus, the method insures a very high output with a very small proportion of rib material in the separate leaf material.

lf necessary, the apparatus of our invention may form part of a stripping train which includes a first stripping or threshing device, 4two groups of separators of the type shown in FiG. 1, a second stripping or threshing device, and two additional groups of separators. In some cases, the train may also include suitable yre-separating devices for the small amounts of residues.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptions should and are `intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of separating lighter particles from heavier particles which together form a mixture of tobacco particles, `comprising introducing a continuous stream consisting of a mixture of lighter and heavier tobacco particles into an ascending non-vertical current of air; reducing the speed of the stream by permitting the current of air to expand whereby some of the heavier particles descend by gravity and leave said current; dividing the remainder of the mixture into a plurality of partial streams and advancing each partial stream in an upwardly extending path with currents of air which are strong enough to entrain the lighter particles but which are too weak to entrain the additional heavier particles contained in said remainder of the mixture so that such additional vheavier particles tend to descend by gravity and form a further stream which hinders the entry of additional heavier particles into the paths of said partial streams; and withdrawing said further stream from the air currents.

2. A method o-f separating tobacco leaves from tobacco ribs which are heavier than and which form a mixture with the leaves, comprising introducing a thin stream of such mixture into an ascending current of air which Hows in an inclined path and which is strong enough to entrain the mixture; reducing the speed of the stream by permitting the current to expand in said path whereby some of the ribs descend by gravity and leave said path; dividing the remainder of the mixture into a plurality of4 partial streams and advancing each partial stream in an ascending current of air which is strong enough to entrain the leave-s but which is too weak to entrain the additional ribs contained in said remainder of the mixture so that such additional ribs tend to descend by gravity and form a further stream which hinders the entry of additional ribs into said partialstreams; and withdrawing said further stream from the air currents.

3. A method of separating lighter particles from heavier particles which together form a mixture, particularly for separating tobacco leaves from ytobacco ribs, comprising the steps of introducing a continuous stream consisting of a mixture of lighter and heavierk particles into an ascending high-velocity current of air ywhich advances in an inclined path; reducing the speed of the stream by permitting gradual expansion of the high-velocity current in said inclined path to such an extent that some of the heavier parti-cles descend by gravity and leave said path; dividing the path into a plurality of upwardly rextending paths so that the current of air is divided into an equal number of partial currents which entrain the l'remainder of the stream into the respective paths with a force which is sutlicient to entrain the lighter particles but which is too weak to entrain the additional heavier particles contained in `said remainder of the stream whereby such additional heavier particles tend to descend and form a further stream which constitutes a barrier against and which thus hinders the entry of additional heavier particles into the paths of said partial streams; and continuously withdrawing said further stream from the air currents.

4. A method of separating lighter particles from heavier particles which together form a mixture, particularly for separating ytobacco leaves from tobacco ribs, comprising the steps of introducing a continuous stream consisting of a mixture of lighter and heavier particles into an ascending high-velocity current of air which advances in an inclined path; reducing the speed of the stream by permitting gradual expansion of the high-velocity current insaid inclined path to such an extent that some of the heavier particles descend by gravity and leave said path; dividing the path into a plurality of upwardly extending paths so that the current of air is divided into an equal number of partial currents which entrain the remainder of the stream into the respective paths with a force which is sufficient to entrain the lighter particles but which istoo weak to entrain the additional heavier particles contained in said remainder of the stream whereby such additional heavier particles tend to descend and form a further stream which constitutes a barrier against and which thu-s hinders the entry of additional heavier particles into the paths of said partial streams; continuously withdrawing said further stream from thevair currents; and subjecting said further stream to the action of an ascending air current which is strong enough to entrain at least some of the lighter particles which might have been cntrained with said further stream but which is too weakto entrain the additional heavier particles so that said .last` mentioned current withdraws from said further stream an additional stream of lighter particles.

5. A method as set forth in claim 4, further comprising the step of merging the partial air currents with said last mentioned air, current so that all of the lighterV particles withdrawn from said mixture form a single stream of lighter particles.

6. A method as set forth in claim 4, further comprising the step of merging the heavier particles which leave said inclined path with the additional heavier particles of said further stream to form a single stream consisting mainly of heavier particles.

7. A method of separating lighter particles from heavier particlesy which together form a mixture of tobacco particles, comprising introducing a continuous stream consisting of a mixture of lighter and heavier tobacco particles into` an ascending non-vertical current of air; re-

ducing the speed of the stream by permitting the current of air to expand whereby some of the heavier particles descend by gravity and leave said current; dividing the remainder ot the mixture into a pair of par-tial streams and advancing each partial stream in an upwardly extending path with currents of air which are strong enough to entrain the lighter particles but which are toor weak to entrain the additional heavier particles contained in said yremainder of the mixture so that such additional heavier particles tend to descendby gravity and form a further stream which constitutes a barrier across said current of air and which hinders the entry of additional heavier particles into the paths of said partial streams by reducing the kinetic energy of the remainder of the mixture; and withdrawing saidfurther stream 'from the air currents.

S. A method of separating tobacco leaves from tobacco ribs which are heavier than and which form a mixture with the leaves, comprising introducing a thin st-reamof such mixture into an ascending current of air which flows in an inclined path and'whi-ch is strong enough to entrain the mixture; reducing the speed of the stream by permitting the current to expand in said. path whereby some of the ribs descend by gravity and leave said path; dividing the remainder ot the mixture into a plurality of partial streams and advancing each partial stream in an ascending current of air which is strong enough to entrain the theleaves but which is too weak to entrain the additional ribs 1contained :in said remainder of the mixture so that such additional ribs tend-to descend by gravity and form a further stream which hinders the entry of `additional ribs into said partial streams; withdrawing said further stream from the -air currents and merging said further stream with the ribs which descend by gravity to form a single stream mainly consisting of heavier particles; and directing against said single stream an ascending current of air which is strong enough to entrain at least som-e lighter particles which might be .contained in said single stream.

9. A method of separating tobacco leaves from tobacco ribs whichl are heavier than and which form a mixture with t-he leaves, comprising introducing a thin stream of such mixture into an ascending current of air which flows in an inclined path and which is strong enough to entrain the mixture; reducing the speed ofthe stream by permitting into an ascending currentl of air which vflows in an inclined path and which is strong enough to entrain the mixture; reducing the speed-of the stream by permitting the current to expand in said ,path whereby some of the ribs descend by gravity and leave said path; dividing the remaindery of thel mixture into a plurality of partial streams and advancing each partial stream in an ascending current of air which is strong enough to entrain Athe leaves but which is too weak to entrain the additional ribs contained in said remainder of the mixture so that such:

additional ribs tend to descend by gravity and form a further stream which hinders the entry'of additional ribs into said partial streams; withdrawing said further stream from the air currents and directing against said further stream -an ascending current of air strong enough to entrain at least some leaves which might khave been entrained with said further stream;,and merging the remainder of said further stream with .the ribs which descend by gravity from said inclined path.

10. Anapparatus for pneumatically separating lighterparticles from heavier particles which together form a mixture, comprising a housing dening an upwardly inclined expansion spacehaving an upper portion and a lower portion; an intake connected tof-the housing and communicating with the lower portion of said space, said intake being arranged to admit into said space a continuous stream of such mixture together with an ascending current of high-velocity air whereby the current entering said space expands sutiiciently to permit descent of some of the `heavier particles; iirst extractor means for withdrawing such descending particles from the lower portion of said space; baflie means provided in said housing above said space and defining a plurality of channels each of which communicates with and extends upwardly from said space so that the remainder of the mixture may be entrained by the air toward said channels with a force sufficient to entrain only the lighter particles whereby the additional heavier particles contained in `the remainder of the mixture tend to descend and form a further stream which hinders the entry of additional heavier particles into said channels; second extractor means adjacent to the upper portion of said space for withdrawing said further stream from the housing; and off-take means for withdrawing lighter parti-cles from said channels.

11. An apparatus for pneumatically separating lighter particles from heavier particles which together form a mixture, comprising a housing defining an upwardly inclined expansion space having an upper portion and a lower portion; an intake including an inclined duct connected to the housing and communicating with the lower portion of said space, said intake being arranged to admit into said space a continuous stream of such mixture to gether with an ascending current of high-velocity air whereby the current entering said space expands sufiiciently to permit descent of some of the heavier particles; first extractor means for withdrawing such descending particles from the lower portion of said space; baliie means provided in said housing above said spa-ce and defining a plurality of channels each of which communica-tes with and extends upwardly from said space so that the remainder of the mixture may be entrained by the air toward said channels with a force sutiicient to entrain only the lighter particles whereby the additional heavier particles contained in the remainder of the mixture tend to descend and form a further stream which hinders the entry of additional heavier particles into said channels, the inclination of said duct being such that an imaginary extension thereof leads into one of said channels; second extractor means adjacent to the upper portion of said space for withdrawing said further stream from the housing; and ofi-take means for withdrawing lighter particles from said channels.

12. An apparatus for pneumatically separating lighter tobacco particles from heavier tobacco particles which together form a mixture, particularly for separating tobacco ribs from tobacco leaves, comprising a housing defining an upwardly inclined expansion space having an upper portion and a lower portion; an intake connected to the housing and communicating with the lower portion of said space, said intake being arranged to admrit into said space a continuous stream of such mixture together with an ascending current of high-velocity air whereby the current entering said space expands sufficiently to permit descent of some of the heavier particles; first extractor means for withdrawing such descending particles from the lower portion of said space; bafiie means provided in said housing above said space and defining a pair of channels each of which communicates with and extends upwardly from said space so that the remainder of the mixture may be entrained by the air toward said channels with a force sufficient to entrain only the lighter particles whereby the additional .heavier particles contained in the remainder of the mixture tend to descend and form a further stream which hinders the entry of additional heavier particles into said channels; second extractor means adjacent to the upper portion of said space for withdrawing said further stream from the housing; and oit-take means for withdrawing lighter particles from said channels.

13. An apparatus for pneumatically separating lighter particles from heavier particles which together form a mixture, comprising a housing defining an upwardly inclined expansion space having an upper portion and a lower portion; an intake connected to the housing and communicating with the lower portion of said space, said intake vbeing arranged to admit into said space a continuous stream of such mixture together with an ascending current of high-velocity air whereby the current entering said space expands sufiiciently to permit descent of some of the heavier particles; first extractor means for withdrawing such descending particles from the lower portion of said space; baiiie means provided in said housing above said space and defining a plurality of channels each of which communicates with and extends upwardly from said space so that the remainder of the mixture may be entrained by the air toward said channels with a force sufficient to entrain only the lighter particles whereby the additional heavier particles contained in the remainder of the mixture tend to descend and form a further stream which hinders the entry of additional heavier particles into said channels; second extractor means adjacent to the upper portion of said space for withdrawing said further stream from the housing; off-take means for withdrawing lighter particles from said channels; a second housing adjacent to said first housing and defining an upwardly extending channel which receives additional heavier particles from said second extractor means, said last mentioned channel having an upper -portion and a lower portion with the latter arranged to admit into said second housing an ascending current of air which is strong enough to entrain at least some of the lighter particles that might have passed through said second extractor means; and off-take means communicating with the upper portion of said last mentioned channel Afor withdrawing lighter particles from said second housing.

14. An apparatus as set forth in claim 13, wherein said second housing comprises adjustable guide walls for varying th-e cross-sectional area of the lower portion of said last mentioned channel.

15. An apparatus as set forth in claim 13, wherein each of said extractor means is a rotary cell wheel extractor and further comprising a common drive motor for said extractors.

16. An apparatus as set forth in claim 13, further comprising adjustable valve means provided on said first mentioned housing for admitting secondary air into the lower portion of said expansion space.

17. An apparatus for pneumatically separating lighter particles `from heavier particles which together form a mixture, comprising two groups of separators each including a housing defining an upwardly inclined expansion space having an upper portion and a lower portion; an intake connected to each housing and communicating with the lower portion of the respective space, said intakes vbeing arranged to admit into said spaces continuous streams of a mixture together with ascending currents of high-Velocity air whereby the currents entering said spaces expand suiciently to permit descent of some of the heavier particles; a pair of first extractor means for withdrawing such descending particles from the lower portions of the respective spaces; baflie means provided in each housing above the respective space and each defining a plurality of channels extending upwardly from and communicating with the respective spaces so that the remainder of the respective mixture may be entrained by the air toward said channels with a force which is sufficient to entrain only the lighter particles whereby the additional heavier particles contained in the remainder of the respective mixture tend to descend and form a further stream which hinders the entry of additional heavier particles into the respective channels; a pair of second extractor means adjacent to the upper portions of the respective spaces for withdrawing said further streams from the respective housings; a pair of oii-take means for withdrawing lighter particles from the channels of the respective housings; and conveying means for leading at least a portion of the further stream which is withdrawn by the second extractor means of one of said housings into the intake of the other housing so that such portion of said last mentioned stream constitutes the mixture which is to be separated in the other housing.

18. An apparatus as set forth in claim 17, wherein said conveying means is arranged to receive heavier' particles which descend in the expansion space of said one housing.

19, Anapparatus as set forth in claim 17, wherein said conveying means comprises a `substantially vertical second housing having a connecting duct arranged to receive the stream Withdrawn by the respective second extractor means, said second housing dening an upwardly extending chamber through which the stream withdrawn through the respective second extractor means descend, means provided at the lower end of said second housing for admitting an ascending current of air into the chamber of said second housing so that such current may entrain at least some of the lighter particies which might have been withdrawn by the respective second extractor means, and off-take means provided at the upper end o said second rhousing for withdrawing lighter particles therefrom.

2Q. An apparatus as set forth in claim 19, wherein all of said housings form a unit of interconnected housings and wherein said second housing is disposed between said .first mentioned housings.

References Cited by the Examiner UNITED STATES PATENTS 3,010,576 ll/196l Harte 209-35 F RANK W. LUTTER, Primary Examiner. 

10. AN APPARATUS FOR PNEUMATICALLY SEPARATING LIGHTER PARTICLES FROM HEAVIER PARTICLES WHICH TOGETHER FORM A MIXTURE, COMPRISING A HOUSING DEFINING AN UPWARDLY INCLINED EXPANSION SPACE HAVING AN UPPER PORTION AND A LOWER PORTION; AN INTAKE CONNECTED TO THE HOUSING AND COMMUNICATING WITH THE LOWER PORTION OF SAID SPACE, SAID INTAKE BEING ARRANGED TO ADMIT INTO SAID SPACE A CONTINUOUS STREAM OF SUCH MIXTURE TOGETHER WITH AN ASCENDING CURRENT OF HIGH-VELOCITY AIR WHEREBY THE CURRENT ENTERING SAID SPACE EXPANDS SUFFICIENTLY TO PERMIT DESCENT OF SOME OF THE HEAVIER PARTICLES; FIRST EXTRACTOR MEANS FOR WITHDRAWING SUCH DESCENDING PARTICLES FROM THE LOWER PORTION OF SAID SPACE; BAFFLE MEANS PROVIDED IN SAID HOUSING ABOVE SAID SPACE AND DEFINING A PLURALITY OF CHANNELS EACH OF WHICH COMMUNICATES WITH AND EXTENDS UPWARDLY FROM SAID SPACE SO THAT THE REMAINDER OF THE MIXTURE MAY BE ENTRAINED BY THE AIR TOWARD SAID CHANNELS WITH A FORCE SUFFICIENT TO ENTRAIN ONLY THE LIGHTER PARTICLES WHEREBY THE ADDITIONAL HEAVIER PARTICLES CONTAINED IN THE REMAINDER OF THE MIXTURE TEND TO DESCEND AND FORM A FURTHER STREAM WHICH HINDERS THE ENTRY OF ADDITIONAL HEAVIER PARTICLES INTO SAID CHANNELS; SECOND EXTRACTOR MEANS ADJACENT TO THE UPPER PORTION OF SAID SPACE FROM WITHDRAWING SAID FURTHER STREAM FROM THE HOUSING; AND OFF-TAKE MEANS FOR WITHDRAWING LIGHTER PARTICLES FROM SAID CHANNELS. 